Whilst a character is part of a unit, both they and the unit (including any other characters that have joined that unit) are treated as a single combined unit for all rules purposes, save for the exceptions listed here.
Source: Warhammer Armies Project: Unofficial 9th Edition (v2.2)
Whilst a character is part of a unit, both they and the unit (including any other characters that have joined that unit) are treated as a single combined unit for all rules purposes, save for the exceptions listed here.